Do a search on the forums for XADataSource. There are a number of threads here with that information. I had a similar issue when I was trying to utilize regular JDBC calls on a local database. Since XADataSource is for transactions across distributed databases, make sure that's what you want to do. If not, you'll need to model the configuration file found at docs/examples/jca/oracle-ds.xml instead of oracle-xa-ds.xml.
Likewise, you will probably need to post some code for others to help you.
Hope that helps.